TWI786954B - Device and method of simultaneously removing flammable gas and nitrous oxide - Google Patents

Abstract

A device and a method of simultaneously removing flammable gas and nitrous oxide are provided. The device includes a thermal oxidation chamber, a high-temperature resistant dust filter and a catalyst tank. The thermal oxidation chamber is for receiving exhaust gas from a processing tool. The exhaust gas includes flammable gas and nitrous oxide, and the thermal oxidation chamber has a first exhaust pipe to emit nitrous oxide and dust generated after thermal-oxidation of the exhaust gas. The high-temperature resistant dust filter receives the dust and nitrous oxide from the first exhaust pipe, wherein the high-temperature resistant dust filter has a filter fiber net and a second exhaust pipe, and the second exhaust pipe is for emitting nitrous oxide. The catalyst tank receives nitrous oxide from the second exhaust pipe, wherein the catalyst tank has a nitrous oxide decomposition catalyst to decompose nitrous oxide into nitrogen gas and oxygen gas.

Description

Device and method for simultaneously removing flammable gas and nitrous oxide

The invention relates to a technology for treating tail gas of a process machine, and in particular relates to a device and method for simultaneously removing flammable gas and nitrous oxide.

In 2016, the total global greenhouse gas emissions have reached 50 billion metric tons of carbon equivalent (CO ₂ e). According to the statistics of greenhouse gas emissions in the 2018 U.S. Environmental Protection Summer Announcement, nitrous oxide (N ₂ O) is the second largest emission. three major greenhouse gases. In particular, N ₂ O is the greenhouse gas that has emitted the most in the semiconductor industry in recent years.

At present, electric hot water washing or combustion water washing is mostly used to treat the process tail gas mainly containing N ₂ O, but when N ₂ O is decomposed by pyrolysis, a large amount of air pollutant NO _X will be emitted. In addition, because N ₂ O is not only used in the semiconductor manufacturing process, it is also used together with flammable gases such as silicon, phosphorus, arsenic, and boron. When these flammable gases are oxidized at high temperature, they will form inorganic dust, resulting in alternative fine suspended particles (PM2.5) pollution.

The invention provides a device for simultaneously removing flammable gas and nitrous oxide, which can process gas with a higher concentration of N ₂ O and simultaneously process flammable gas.

The present invention also provides a method for removing flammable gas and nitrous oxide at the same time, which can decompose _N2O into _N2 and _O2 to achieve zero pollution discharge, and prevent the dust produced by high temperature oxidation of flammable gas from being discharged into outside world.

The device for simultaneously removing flammable gas and nitrous oxide of the present invention includes a heating oxidation chamber, a high temperature resistant dust filter and a catalyst tank. The heating and oxidation chamber is used to receive the exhaust gas from the processing equipment. The tail gas contains flammable gas and nitrous oxide, wherein the heating oxidation chamber has a first exhaust pipe to discharge nitrous oxide and dust generated by thermal oxidation of the tail gas. The high-temperature-resistant dust filter receives dust and nitrous oxide from the first exhaust pipe, wherein the high-temperature-resistant dust filter has a filter fiber net and a second exhaust pipe, and the second exhaust pipe is used to discharge nitrous oxide. Dinitrogen. The catalyst tank receives the nitrous oxide from the second exhaust pipe, wherein the catalyst tank has a nitrous oxide decomposition catalyst to decompose the nitrous oxide into nitrogen (N ₂ ) and oxygen (O ₂ ).

The method for simultaneously removing flammable gas and nitrous oxide of the present invention is to use the above-mentioned device, first use the above-mentioned heating and oxidation chamber to heat the tail gas from the process machine, wherein the tail gas contains flammable gas and nitrous oxide, and the The above-mentioned flammable gas is thermally oxidized into dust. Then, use the above-mentioned high-temperature-resistant dust filter to filter the dust from the heating oxidation chamber, and then use the above-mentioned catalyst tank to decompose the nitrous oxide discharged from the high-temperature-resistant dust filter into nitrogen and oxygen.

Based on the above, the device according to the present invention can first process flammable gases containing silicon, phosphorus, arsenic, and boron with a heating and oxidation chamber, and then filter out the inorganic dust generated by the process end and the above-mentioned heating and oxidation chamber through a high-temperature dust filter, and finally, With the catalyst tank containing nitrous oxide decomposition catalyst, N ₂ O is completely decomposed into nitrogen and oxygen to achieve zero pollution emissions, so as to solve the harmful side effects of a large amount of NO _x produced by the high-temperature thermal decomposition method in the past to treat N ₂ O product defects, and filter the dust formed by the oxidation of other process gases.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

The attached drawings in the following embodiments are for more complete description of the embodiments of the present invention, however, the present invention can still be implemented in many different forms, not limited to the described embodiments. In addition, the relative distances, sizes and positions of various devices or conduits may be reduced or exaggerated for clarity.

Fig. 1 is a schematic diagram of a device for simultaneously removing flammable gas and nitrous oxide according to an embodiment of the present invention.

Referring to FIG. 1 , the device 100 of this embodiment basically includes a heating and oxidation chamber 102 , a high temperature resistant dust filter 104 and a catalyst tank 106 . The heating oxidation chamber 102 is used to receive exhaust gas from a process tool (not shown), wherein the exhaust gas may include flammable gas and nitrous oxide (N ₂ O). The heating and oxidation chamber 102 has a first exhaust pipe 108 to discharge the dust produced by thermal oxidation of N ₂ O and tail gas.

The high-temperature dust filter 104 receives the dust and _N2O from the first exhaust pipe 108, and is provided with a high-temperature-resistant filter fiber mesh 112, and the operating temperature of the high-temperature-resistant dust filter 104 is from normal temperature to high temperature. Such as between 20°C~750°C. The high temperature resistant dust filter 104 also has a second exhaust pipe 110 to discharge N ₂ O. As shown in Figure 1, the position where the first exhaust pipe 108 is connected to the high-temperature-resistant dust filter 104 is generally lower than the exit position of the second exhaust pipe 110, allowing the dust and _N2O in the first exhaust pipe 108 to enter After the high-temperature dust filter 104 , the dust is blocked by the filter fiber net 112 and falls to the bottom of the high-temperature dust filter 104 , while N ₂ O is discharged from the second exhaust pipe 110 above through the filter fiber net 112 . In one embodiment, the material of the filter fiber net 112 is a high temperature resistant material, which is not particularly limited, such as ceramic (Al ₂ O ₃ ) fiber, polytetrafluoroethylene (PTFE) fiber, polyimide (PI) fiber , aromatic polyamide (Aramid) fiber, polyphenylene sulfide (PPS) fiber; filter fiber net 112 has high porosity, for example, when the density of filter fiber net is about 0.4 grams/cubic centimeter, the diameter of ceramic fiber is about 2-3 μm, can filter out dust with a particle size of 100nm-1000nm.

The catalyst tank 106 receives N ₂ O from the second exhaust pipe 110, and has a nitrous oxide decomposition catalyst (not shown) in the catalyst tank 106, which can decompose N ₂ O into nitrogen (N ₂ ) and Oxygen ( _O2 ). In one embodiment, the catalyst tank 106 is filled with the nitrous oxide decomposition catalyst particles, the particle diameter of the catalyst particles can be between 2 mm to 5 mm, and the porosity in the catalyst tank 106 is, for example, 60%. ~70%. The aforementioned "porosity" is defined as the water weight after filling the catalyst/the water weight of the unfilled catalyst x 100% under a fixed volume. If the catalyst particle size or the porosity of the catalyst tank is too small, it is not conducive to the passage of gas and affects the treatment efficiency. In terms of catalyst materials, in one embodiment, the nitrous oxide decomposition catalyst can be a composite catalyst of iron oxide and aluminum oxide, and the matching catalyst carrier can be titanium dioxide, generally referred to as iron-aluminum-titanium catalyst, wherein, The ratio of the total moles of iron oxide and alumina to the moles of titanium dioxide is 3.5:1 to 2.5:1, and the molar ratio of iron oxide and alumina can be, for example, 2.5:1 to 1.5:1. However, the present invention is not limited thereto, and the above-mentioned nitrous oxide decomposition catalyst may also include platinum (Pt), palladium (Pd), rhodium (Rh), copper (Cu), nickel (Ni), cobalt (Co), Manganese (Mn), silver (Ag), molybdenum (Mo), tungsten (W), vanadium (V), lanthanum (La) and other metal elements. However, compared with noble metal elements, the use of iron-aluminum-titanium catalyst can greatly reduce the processing cost. The catalyst tank 106 may further include a third exhaust pipe 114 for outputting decomposed N ₂ and O ₂ .

Please continue to refer to FIG. 1 , the device 100 of this embodiment can also be provided with a first pump 116 to increase the pressure of the exhaust gas entering the heating and oxidation chamber 102 , for example, the first pump 116 is connected to the input pipe 118 of the exhaust gas. A second pump 120 may also be provided at the third exhaust pipe 114 to provide negative pressure to the third exhaust pipe 114 to facilitate the flow of gas in the catalyst tank 106 . Moreover, in order to detect the effects of each device in real time, a sampling hole 122a can be added in the first exhaust pipe 108, a sampling hole 122b can be added in the second exhaust pipe 110, a sampling hole 122c can be added in the third exhaust pipe 114, and a sampling hole 122c can be added in the exhaust gas pipe 110. The input pipe 118 is provided with a sampling hole 122d. The sampling hole 122a can be used to sample and detect the gas (flammable gas and N ₂ O) concentration, so as to confirm whether the flammable gas is oxidized and removed. The sampling hole 122b can be used to take a sample and detect whether the dust is filtered out. If the dust content exceeds a preset value, the filter fiber net 112 must be replaced. The sampling hole 122c can be used to sample and detect whether the N ₂ O is completely decomposed into N ₂ and O ₂ . If the N ₂ O treatment efficiency is less than 90%, it is necessary to replace the catalyst, overhaul or replace the device 100 . The sampling hole 122d can be used to sample and detect the gas (flammable gas and N ₂ O) concentration in the exhaust gas as an initial value.

FIG. 2 is a step diagram of simultaneously removing flammable gas and nitrous oxide according to another embodiment of the present invention.

Please refer to FIG. 2 , this embodiment uses the device 100 of the previous embodiment. First, step 200 is performed, and the above-mentioned heating and oxidation chamber (102 as shown in Figure 1) is used to heat the exhaust gas from the process machine, such as the semiconductor process machine, wherein the exhaust gas contains flammable gas and N ₂ O, and the flammable body is heated. Oxidation into dust, wherein the thermal oxidation temperature is, for example, between 450°C and 750°C. The flammable gas includes a gas containing at least one of silicon, phosphorus, arsenic and boron, such as SiH ₄ , Si ₂ H ₆ , PH ₃ , AsH ₃ or B ₂ H ₆ . Before using the heating and oxidation chamber to heat the tail gas from the process machine, the first pump (116 as shown in Figure 1) can also be used to feed nitrogen to pressurize the tail gas, wherein the flow rate of nitrogen can be controlled at 500 LPM Next, it is beneficial to the reaction of N ₂ O entering the back-end catalyst tank (eg 106 in FIG. 1 ). Since the flow into the heating and oxidation chamber (such as 102 in FIG. 1 ) is related to the pressure, the pressure in the heating and oxidation chamber (such as 102 in FIG. 1 ) can be controlled between 650 torr and 750 torr.

Then, proceed to step 202, using a high temperature resistant dust filter (such as 104 in FIG. 1) to filter the dust from the heating and oxidation chamber (such as 102 in FIG. 1). In this road step 202, there is no need to control the temperature or the flow rate in particular, and the gas entering the high-temperature-resistant dust filter (104 as shown in Figure 1) can naturally enter the second exhaust pipe (such as 112 as shown in Figure 1) through the filter fiber net (112 as shown in Figure 1). 110 of Figure 1).

Next, step 204 is performed, using the catalyst tank (eg 106 in FIG. 1 ) to decompose the N ₂ O discharged from the high temperature resistant dust filter (eg 104 in FIG. 1 ) into N ₂ and O ₂ . The operating temperature of the catalyst tank (eg, 106 in FIG. 1 ) is, for example, between 450°C and 600°C. Since the device of the present invention integrates the equipment for thermally oxidizing flammable gases and the equipment for decomposing nitrous oxide, and adds a filter between the two, it can continuously treat the tail gas of the process and save processing time. with the effect of improving removal efficiency.

The following experiments are listed to verify the efficacy of the present invention, but the present invention is not limited to the following content.

<Experimental Example 1>

Among the flammable gases containing silicon, phosphorus, arsenic, and boron used in semiconductor factories, SiH ₄ is used in the largest amount, and these flammable gases can break bonds and decompose at a temperature of 500 °C, so SiH ₄ was used as a test in Experimental Example 1. gas.

First, set up the detection equipment as shown in Figure 3 to heat the chamber with a volume of about 1900 L to 500°C by electric heating or combustion, and then use a mass flow controller (MFC) to feed pure SiH ₄ and dilute it with different flows of pure N ₂ After treatment in the heating oxidation chamber, use Fourier transform infrared spectroscopy (FTIR) to analyze the concentration of SiH ₄ at the front and rear ends of the heating oxidation chamber and calculate the destruction removal efficiency (Destruction and Removal Efficiency, DRE). The experimental results are shown in Table 1 and FIG. 4 below.

Table 1 heating oxidation chamber temperature 500°C Inlet port N ₂ flow 52.5 LPM 62.5 LPM 72.5 LPM DRE 99.8% 99.7% 99.5%

It can be seen from FIG. 4 and Table 1 that the heated oxidation chamber of the device of the present invention can effectively remove SiH ₄ and oxidize it into silicon oxide. Moreover, the lower the flow rate, the more concentrated the SiH ₄ entering the heated oxidation chamber, and the higher the DRE.

<Experimental Example 2>

The peak particle size of powdered SiO ₂ produced by SiH ₄ after high-temperature oxidation is about 200 nm~300 nm, and the higher the filtration temperature, the better the filtering effect. Therefore, in this experiment, SiO ₂ with a particle size of about 200 nm was used at room temperature The filtration experiment is carried out to test the filtration effect of the high temperature resistant dust filter.

First, set up the detection equipment as shown in Figure 5, set up a ceramic filter in the 45 L high temperature resistant dust filter, the gas flow rate that can be processed is below 350 LPM, and then use PALAS (dust aerosol generation Add 200 nm SiO ₂ powder at constant speed, sample and measure the dust concentration at the inlet and outlet of the high temperature dust filter, and calculate its dust removal efficiency (Particle Removal Efficiency, PRE). The experimental results are shown in Table 2 below.

。 Table 2 Inlet port flow (Q _in ) 252 LPM 231 LPM 215 LPM 54 LPM 61 LPM Inlet port concentration (C _in ) 88.69 mg/ ^m3 124.03 mg/ ^m3 127.05 mg/ ^m3 41.57 mg/ ^m3 53.56 mg/ ^m3 Outlet flow (Q _out ) 323 LPM 272 LPM 248 LPM 113 LPM 135 LPM Outlet concentration (C _out ) 3.15 mg/ ^m3 0.26 mg/ ^m3 2.33 mg/ ^m3 0.11 mg/ ^m3 0.19 mg/ ^m3 PRE 95.45% 99.75% 97.88% 99.44% 99.21% PRE _Avg 97.69% 99.33% in

.

It can be obtained from Table 2 that the high temperature resistant dust filter of the device of the present invention has a PRE up to more than 97% even at normal temperature. Therefore, effective filtration can be achieved without special control of the temperature in the high-temperature-resistant dust filter when receiving dust from the heating oxidation chamber.

<Experimental example 3>

In order to simulate the concentration of N ₂ O tail gas in the real process of semiconductor factories, this experiment uses iron-aluminum-titanium catalysts to decompose N ₂ O with a concentration of about 20%.

First, set up the detection equipment as shown in Figure 6. The volume of the catalyst tank is about 20 ml, which is filled with iron-aluminum-titanium catalyst particles, the particle size is between 2 mm and 5 mm, and the porosity in the catalyst tank is about The molar ratio of iron oxide and aluminum oxide in the iron-aluminum-titanium catalyst to the total molar number of titanium dioxide is about 3:1, and the molar ratio of iron oxide and aluminum oxide is about 2:1. Then test with the following conditions. 1. N ₂ O concentration at inlet: ~ 20% 2. Gas flow: 648.2 sccm (129.9 sccm N ₂ O, 518.3 sccm N ₂ ) 3. Reaction temperature: 500 °C 4. GHSV: 1944.6 h ^-1 (residence time ~1.9 seconds) 5. Line speed: 10.2 cm/s

）。而且，並未測到NO與NO ₂。 Measure the N ₂ O concentration at the outlet of the N ₂ O catalyst chamber to be about 7837 ppm, and it can be calculated that DRE= 96.1% (

). Also, NO and NO ₂ were not detected.

In summary, the device of the present invention is composed of a continuously connected heating and oxidation chamber, a high temperature resistant dust filter and a catalyst tank, so the heating and oxidation chamber can be used to treat flammable gases such as silicon, phosphorus, arsenic and boron, and then through The high-temperature resistant dust filter filters out the dust generated by the process end and the above-mentioned heating and oxidation chamber, and finally uses the catalyst tank to completely decompose N ₂ O into nitrogen and oxygen, so as to achieve the result of zero pollution emission and solve the problem of traditional high temperature The problem of producing a large amount of harmful by-products of NO _x in the treatment of N ₂ O by thermal decomposition can also be used to deal with flammable gases in other processes.

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention should be defined by the scope of the appended patent application.

100: device 102: heating oxidation chamber 104: High temperature resistant dust filter 106: Catalyst tank 108: The first exhaust pipe 110: Second exhaust pipe 112: Filtration fiber net 114: The third exhaust pipe 116: The first pump 118: input tube 120:Second pump 122a, 122b, 122c, 122d: sampling holes 200, 202, 204: steps MFC: mass flow controller FTIR: Fourier Transform Infrared Spectrometer

Fig. 1 is a schematic diagram of a device for simultaneously removing flammable gas and nitrous oxide according to an embodiment of the present invention. FIG. 2 is a step diagram of simultaneously removing flammable gas and nitrous oxide according to another embodiment of the present invention. FIG. 3 is a schematic diagram of detection equipment for the heating and oxidation chamber of Experimental Example 1. FIG. Fig. 4 is a graph showing the change of SiH ₄ concentration with time in Experimental Example 1. FIG. 5 is a schematic diagram of testing equipment for the high-temperature-resistant dust filter of Experimental Example 2. FIG. FIG. 6 is a schematic diagram of detection equipment for the catalyst tank of Experimental Example 3. FIG.

100: device

102: heating oxidation chamber

104: High temperature resistant dust filter

106: Catalyst tank

108: The first exhaust pipe

110: Second exhaust pipe

112: Filtration fiber net

114: The third exhaust pipe

116: The first pump

118: input tube

120:Second pump

122a, 122b, 122c, 122d: sampling holes

Claims (17)

A device for removing flammable gas and nitrous oxide at the same time, comprising: a heating oxidation chamber that receives tail gas from a process machine, the tail gas contains flammable gas and nitrous oxide, wherein the heating oxidation chamber has a first an exhaust pipe to discharge the dust and nitrous oxide produced by thermal oxidation of the tail gas; a high temperature resistant dust filter to receive the dust and nitrous oxide from the first exhaust pipe, wherein the The high-temperature resistant dust filter has a filter fiber net and a second exhaust pipe, and the second exhaust pipe is used to discharge nitrous oxide; and a catalyst tank receives the nitrous oxide from the second exhaust pipe, Wherein the catalyst tank has a nitrous oxide decomposition catalyst to decompose the nitrous oxide into nitrogen (N ₂ ) and oxygen (O ₂ ). The device for simultaneously removing flammable gas and nitrous oxide as described in Claim 1, wherein the operating temperature of the high-temperature-resistant dust filter is between 20°C and 750°C. The device for simultaneously removing flammable gas and nitrous oxide as described in claim 1, wherein the nitrous oxide decomposition catalyst includes an iron-aluminum-titanium catalyst, and the iron oxide and nitrous oxide in the iron-aluminum-titanium catalyst The ratio of the total molar number of aluminum to the molar number of titanium dioxide is 3.5: 1 to 2.5: 1, and the molar ratio of iron oxide to aluminum oxide in the iron-aluminum-titanium catalyst is 2.5: 1 to 1.5: 1. The device for simultaneously removing flammable gas and nitrous oxide as described in Claim 1, wherein the porosity in the catalyst tank is 60% to 70%. The device for simultaneously removing flammable gas and nitrous oxide as described in Claim 1, wherein the particle size of the nitrous oxide decomposition catalyst is between 2 mm and 5 mm. The device for simultaneously removing flammable gas and nitrous oxide as described in Claim 1 further includes a first pump to increase the pressure of the tail gas entering the heating oxidation chamber. The device for simultaneously removing flammable gas and nitrous oxide according to claim 1, wherein the position where the first exhaust pipe is connected to the high-temperature-resistant dust filter is lower than the outlet of the second exhaust pipe Location. The device for simultaneously removing flammable gas and nitrous oxide according to claim 1, wherein the catalyst tank includes a third exhaust pipe for outputting nitrogen and oxygen. The device for simultaneously removing flammable gas and nitrous oxide as described in Claim 8 further includes a second pump to provide negative pressure to the third exhaust pipe. A method for simultaneously removing flammable gas and nitrous oxide using a device as described in any one of claims 1 to 9, comprising: using the heating and oxidation chamber to heat the tail gas from the process machine, wherein the tail gas contains flammable gas and nitrous oxide, and the flammable gas is thermally oxidized into dust; filtering said dust from said heated oxidation chamber using said refractory dust filter; and The catalyst tank is used to decompose the nitrous oxide discharged from the high temperature resistant dust filter into nitrogen and oxygen. The method for simultaneously removing flammable gases and nitrous oxide as described in Claim 10, wherein the thermal oxidation temperature is between 450°C and 750°C. The method for simultaneously removing flammable gas and nitrous oxide according to claim 10, wherein the flammable gas includes a gas containing at least one of silicon, phosphorus, arsenic, and boron. The method for simultaneously removing flammable gas and nitrous oxide according to claim 10, wherein the flammable gas includes SiH ₄ , Si ₂ H ₆ , PH ₃ , AsH ₃ or B ₂ H ₆ . The method for simultaneously removing flammable gases and nitrous oxide as described in Claim 10, wherein the pressure of the heating and oxidation chamber is between 650 torr and 750 torr. The method for simultaneously removing flammable gases and nitrous oxide as described in claim item 10, wherein before using the heating and oxidation chamber to heat the tail gas from the exhaust gas, it further includes using the first pump to feed nitrogen to the Exhaust pressurization. The method for simultaneously removing flammable gas and nitrous oxide as described in Claim 15, wherein the flow rate of the nitrogen gas is below 500 LPM. The method for simultaneously removing flammable gas and nitrous oxide as described in Claim 10, wherein the operating temperature of the catalyst tank is between 450°C and 600°C.

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